There is a project called SCALE that allows building CUDA code natively for AMD GPUs. It is designed as a drop-in replacement for Nvidia CUDA, and it is free for personal and educational use.

You can find out more here: https://docs.scale-lang.com/stable/

There are still many things that need implementing, most important ones being cuDNN and CUDA Graph API, but in my opinion, the list of things that are supported now is already quite impressive (and keeps improving): https://github.com/spectral-compute/scale-validation/tree/ma...

Disclaimer: I am one of the developers of SCALE.